U.S. Floods of 1985

By C.A. Perry, B.N. Aldridge, and H.C. Ross of the USGS

Floods occurred in the Northeastern and Central States due to a series of winter storms starting in December 1984 and continuing through April 1985. Alternate periods of freezing and thawing from December to April kept rivers high from Illinois to New York. Discharges on the Elkhart River at Goshen, Indiana, and on the La Moine River at Colmar, Illinois, were near the 100-year recurrence interval.

As much as 6.9 in. of rainfall, combined with unseasonably warm temperatures and rapidly melting snow, caused extensive flooding throughout northern New York from December 29 through January 2. Maximum discharges at six streamflow-gaging stations in the Black and Salmon River Basins had recurrence intervals greater than or equal to 100 years.

Cheyenne, Wyoming, had its worst flood in more than 120 years on August 1. During the afternoon, a moderate thunderstorm developed southeast of Cheyenne, but the storm increased in intensity as it moved into the city during the early evening. Torrential rain, golf-ball-sized hail, and 70-mi/hr winds were produced by the storm. Seven inches of rain fell in less than 24 hours. The discharge for Dry Creek in Cheyenne greatly exceeded the estimated 100-year recurrence interval. The flood caused 12 deaths and $61.1 million in damages. The city was declared a Federal disaster area.

On October 6, a tropical depression stalled and caused intense precipitation over southern Puerto Rico. As much as 24.6 in. of rain fell in a 24-hour period (National Oceanic and Atmospheric Administration, 1985). The most severe flooding occurred along the southern coast. Most of these maximum discharges had recurrence intervals of 50 years or greater. There were many devastating landslides that resulted from the intense rains as well. The worst landslide ravaged a populated area northwest of the city of Ponce. Deaths totalled 170, and damages of $125 million occurred.

The 1985 hurricane season was longer than normal with six hurricanes hitting the United States. They were Hurricanes Bob, Danny, Elena, Gloria, Juan, and Kate. The first hurricane to make landfall was Hurricane Bob in Florida on July 23, and the last was Hurricane Kate, striking Florida, Georgia, and South Carolina on November 16.

Hurricane Elena made landfall in Mississippi on September 2. Elena followed an erratic path, first entering the Gulf of Mexico heading for the Louisiana coast when it turned and threatened the Florida coast for 2 days before turning again and hitting land in Mississippi. The storm quickly moved through Mississippi and Louisiana and finally dissipated over Missouri. Coastal flooding was severe in Florida. Residents of low areas were ordered to evacuate along most of the west coast of Florida.

Hurricane Gloria developed off the west coast of Africa and eventually became the first hurricane to strike New England since 1960. Hundreds of thousands of people were evacuated from coastal areas between North Carolina and Massachusetts because of expected high winds and tidal flooding. Although tidal flooding from Gloria was severe, the riverine flooding was minor because the hurricane did not produce large amounts of rain.

Similar to Hurricane Elena, Hurricane Juan followed an erratic path in the Gulf of Mexico. The storm formed in the central Gulf of Mexico on October 25, then moved northeast toward Louisiana. The storm veered toward Texas before turning back toward Louisiana where it finally made landfall on October 29. On October 30, the storm again moved offshore and made landfall in Florida on October 31. As a result of Juan's slow meandering path, the storm produced excessive rainfall. Despite the large amount of rain, there was minimal riverine flooding in the Coastal States. Storm surges, however, caused severe coastal flooding in Louisiana and Mississippi.

In November, remnants of Hurricane Juan combined with a low-pressure system moving in from the west and then combined with a stalled system over the Appalachian Mountains. The resultant moisture-laden weather system caused severe flooding in large areas of West Virginia and Virginia, and significant flooding in smaller parts of Maryland and Pennsylvania. New maximum discharges were recorded at 63 streamflow-gaging stations, all exceeding 100-year recurrence intervals. The flooding in West Virginia was called the worst in that State's history, with 38 lives lost and $578 million in damages. The Cheat River and South Branch Potomac River Basins were the hardest hit. Overall, the storm was the fourth most costly hurricane-type storm in United States history (to 1985), with 62 lives lost and $1,400 million in damages.

Source: USGS.